Sound card static noise (mic)

Hey, multiple people keep telling me on Skype that i have a really high static background noise, even when i muted my headset mic. So i guess its a sound card or a driver issue, but i cant seem to fix it. Turning of mic boost does not help. Using on-board soundcard from Asus P8P67 Pro and a Steelseries Siberia V2 as headset. I tried reinstalling the drivers on the asus website multiple times, without success.

Does it happen on any other devices like over wifi? I had a similar problem once before and it turned out that a wire had come loose in the junction box to my house and it was causing a dirty signal. If nothing you do now seems to cure it, I recommend calling your ISP for an engineer.